The invention relates to a formulation and method of using same for improving well productivity in hydrocarbon reservoirs.
Improvement in productivity of heavy and extra heavy oil wells such as those found in the Orinoco River Belt in Venezuela is clearly desirable. Some of the largest reservoirs of heavy and extra heavy oil in the world are in Venezuela and hold oil having API gravity within the range of 6 to 16. Unfortunately, the production rate of much of this oil is unacceptable.
It is a high concern in the exploitation of heavy and extra heavy oil reservoirs to increase productivity during the well lifetime. With these wells, primary cold production schemes are quickly abandoned in favor of thermal methods to improve well flowability by reducing oil viscosity in the reservoir. These processes are costly and also still produce a low output in terms of final recovery. They also have serious problems of production of sour gas such as H2S and CO2 which are very costly to address. Such thermal recovery methods typically produce final oil recovery below 35-40%.
Venezuelan heavy and extra heavy Orinoco River Belt oil sandstones are exceptional reservoirs. 60% of the reservoirs of this type have a KH/U value between 40 and close to 1,000 in very many cases. Unlike other reservoirs, however, the oil in Venezuelan extra heavy oil reservoirs is flowable at reservoir conditions.
Even these wells, however, have a final recovery by cold production which is very low and perhaps in most cases below three (3) percent of the original oil in place. The conditions for flow of oil in those reservoirs, with even excellent petrophysical properties, are very unfavorable to the flow of oil. The components of the heavy and extra heavy oil, particularly the asphaltenes in natural form in the native oil, are capable by natural fluid-rock interactions of generating an oil-wet condition at the surface of the natural mineral components of the sandstone. This produces the most adverse conditions to flow of oil in a porous media. This is a natural oil-wet condition of the reservoir media, which is a completely different condition as compared to formation damage in the well resulting from drilling or production activities, which could also happen in the well.
The need exists for improvement in production rates from wells producing from formations containing heavy and extra heavy wells, particularly those which contain asphaltenes and other hydrocarbons which lead to oil wet flow environments.